1. Field of the Invention
The present invention relates to a process for loading a lathe with bars to be machined, and more specifically to a process where the bars are held in a gripping unit of the lathe, each bar being guided in a guiding tube formed of two parts and in which a bar is pushed toward a head-stock of the lathe by a push-piston. A new bar to be machined is introduced laterally in the guide-bar device after the two guiding tube parts have been opened. The invention further relates to a loading device for loading a lathe with bars to be machined and more specifically to a loading device in which the guide-bar device is in the form of a tube for rotatingly supporting the bar to be machined in machine-oil which provides hydrodynamic support for the bar. Feeding of the bar in the tube is provided by a push-piston which supports the rear part of the bar and which is hydraulically controlled. The guiding tube is formed of two parts capable of being separated for laterally inserting a new bar to be machined in the guiding tube.
2. Background
Hydraulic guide-bar devices are known which are manually loaded and which permit great speeds of rotation of the bars to be attained. The remnant of a bar which has been machined is generally removed by a feed collet on the head-stock of the lathe. However, such non-automatic machines have long idle periods to accomodate stepping of the spindle and manual insertion of the next bar, all of which considerably increases the loading time and reduces the output of the machine.
Such a bar loading device for a machine-tool is described in U.S. Pat. No. 2,577,203 in which a guide-bar device is disclosed which comprises a segment pivoted to the end of a rocker arm. During normal working of the device the bar which is in the lowest portion of a bar magazine rests on a surface of the segment and a slide for holding the bars in the magazine is disengaged. At the time of loading, the segment is pivoted which opens the guide-bar tube and the lowest bar of the magazine falls laterally into the tube while the slide is advanced by a spring in order to hold the other bars in the magazine. A push-piston, controlled pneumatically, feeds the bar in the tube. At the time of loading the push-piston is retracted by vacuum. However, the guide bar tube described in the above-noted patent is not subjected to the pressure of machine oil for hydrodynamically supporting the bar to be machined, thus limiting the speed of rotation of the bar within guide-bar device.